This process of illuminating each FRU's outer FRU fault LED is repeated until the outermost FRU is reached; resulting in a path of amber fault LEDs that can be followed to find the innermost FRU that ...This process of illuminating each FRU's outer FRU fault LED is repeated until the outermost FRU is reached; resulting in a path of amber fault LEDs that can be followed to find the innermost FRU that needs attention. FRU fault LEDs that are not visible from the outside of the system remain on when the containing FRU (usually a controller or IOXM) is removed from the chassis.